Add initial support for persisting premium lists to Cloud SQL (#285)

* Add initial support for persisting premium lists to Cloud SQL

This adds support to the `nomulus create_premium_list` command only; support for
`nomulus update_premium_list` will be in a subsequent PR.

The design goals for this PR were:
1. Do not change the existing codepaths for premium lists at all, especially not
   on the read path.
2. Write premium lists to Cloud SQL only if requested (i.e. not by default), and
   write to Datastore first so as to not be blocked by errors with Cloud SQL.
3. Reuse existing codepaths to the maximum possible extent (e.g. don't yet
   re-implement premium list parsing; take advantage of the existing logic), but
   also ...
4. Some duplication is OK, since the existing Datastore path will be deleted
   once this migration is complete, leaving only the codepaths for Cloud SQL.

* Refactor out common logic

* Add DAO test

* Add tests for parsing premium lists

* Use containsExactly

* Code review changes

* Format

* Re-generate schema

* Fix column names

* Make some tests pass

* Add SQL migration scripts

* Fix test errors

db/src/main/resources/sql/flyway/V5__update_premium_list.sql

@@ -0,0 +1,17 @@
+-- Copyright 2019 The Nomulus Authors. All Rights Reserved.
+--
+-- Licensed under the Apache License, Version 2.0 (the "License");
+-- you may not use this file except in compliance with the License.
+-- You may obtain a copy of the License at
+--
+--     http://www.apache.org/licenses/LICENSE-2.0
+--
+-- Unless required by applicable law or agreed to in writing, software
+-- distributed under the License is distributed on an "AS IS" BASIS,
+-- WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+-- See the License for the specific language governing permissions and
+-- limitations under the License.
+
+alter table "PremiumList" add column if not exists name text not null;
+
+create index if not exists premiumlist_name_idx ON "PremiumList" (name);